The Nigerian man known as the "underwear bomber" pleaded guilty Wednesday to trying to blow up a Detroit-bound plane in 2009.

During a Christmas Day flight, a device hidden in Umar Farouk Abdulmutallab's underwear caused smoke and fire, but did not actually explode.

He told the court he tried to commit the act of terrorism in retaliation for the killing of Muslims around the world. Abdulmutallab called the bomb a "blessed weapon to save the lives of innocent Muslims."

He pleaded guilty to eight charges, including conspiracy to commit terrorism and attempted use of a weapon of mass destruction.

Abdulmutallab told investigators he was working for al Qaeda in Yemen.